SHOW CREATE FUNCTION myFun1;
Related explanations of Mysql functions
Meaning: A set of pre-compiled SQL statements, which can be understood as batch statements
Function:
Improve code reusability
Simplify operations
Reduce the number of compilations and connections to the database server, improving efficiency
The difference between stored procedures:
Stored procedures: There can be 0 returns or multiple returns, suitable for Batch insert, batch update
Function: There is only one return, suitable for processing data and returning a result
1. Function syntax
1 . Create
DELIMITER $ CREATE FUNCTION 函数名(参数列表) RETURNS 返回类型 BEGIN 函数体 END$ DELIMITER ;
Note:
The parameter list contains two parts: Parameter name Parameter type
- ## The return value type must be declared at the beginning of #.
- There must be a
return statement in the function body, otherwise an error will be reported
- Use the delimiter statement to set the end mark
SELECT 函数名(参数列表)
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function. Since the function has a return value, you can use select. Print out this value. ==========2. Case demonstration1. Return function without parametersCase: return student table The total number
SELECT 函数名(参数列表)
1.1 Create the function
DELIMITER $ CREATE FUNCTION myFun1() RETURNS INT BEGIN DECLARE num INT DEFAULT 0; #定义一个变量 SELECT COUNT(*) INTO num #赋值 FROM student; RETURN num; #返回值 END $ DELIMITER ;
1.2 Call the function
SELECT myFun1();
2.1 Create function
DELIMITER $ CREATE FUNCTION myFun2(stuName VARCHAR(20)) RETURNS INT BEGIN DECLARE grade INT DEFAULT 0; #定义变量 SELECT s.grade INTO grade #赋值 FROM student s WHERE s.name = stuName; RETURN grade; #返回 END $ DELIMITER ;
2.2 Call
SELECT myFun2('盖伦');
SHOW CREATE FUNCTION myFun1;
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4. Delete functionsSHOW CREATE FUNCTION myFun1;
DROP FUNCTION myFun2;
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##Spark SQL implements log offline batch processingsql Compare the time difference between two adjacent recordsDROP FUNCTION myFun2;
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